Firmware interfaces for computers, such as BIOS (Basic Input/Output System) and UEFI (Unified Extensible Firmware Interface), operate as interpreters between the operating system and the computer's firmware. BIOS or UEFI interfaces may be used at computer startup to initialize the hardware components and to start the operating system that is stored on the computer's hard drive. BIOS boots by reading the first sector on a hard disk and executing it; this boot sector in turn locates and runs additional code. UEFI boots by loading EFI program files (i.e., files having the .efi filename extensions) from a partition on the hard disk, known as the EFI System Partition (ESP). The EFI boot loader programs can take advantage of EFI boot services for things such as reading files from the hard disk.
Typically, BIOS or UEFI updates require a system reboot that results in downtime for users. Such reboots create a challenge coordinating downtime across a very large number servers in a distributed computing environment, such as a datacenter or cloud services network.